Proton is the positive charged particle in the nuclei of atoms that can be extracted from hydrogen gas via ionization. The ionized protons are further accelerated and guided with electromagnetic field to a high speed close to light as the high energy proton beam, in other words, a hypersonic missile. In addition, proton shows barely energy loss upon traveling through matters. It preferentially deposit energy at the end of the path. This enables proton to deliver a compact dose of radiation to a tumor directly and reduces dose to normal tissues, like a Ninja bomb. As the advanced modality in the cancer-fighting arsenal, proton triumphs over X-ray (aka photon beam) in its depth dose distribution nature. The benefits are like the ripple effect: with optimal cancer targeting comes least damage on healthy tissue and less severe side effects, hence a better outcome. By and large, proton therapy peculiarly suits kids, youngsters, elders, and recurrent cancer patients.